Conventionally, flush toilets have been known in which, as set forth in Japanese Patent 2953002 (Patent Document 1), a direct connection is made to a water main, and without the use of a tank the bowl portion is flushed using water main pressure by supplying flush water from a rim water spouting port provided on the rim of a toilet bowl portion, and from a jet water spouting port provided on the bottom portion of the bowl portion, which spouts water toward a drain trap pipe.
In addition, flush toilets have been known in which, as set forth in Patent Document 2, rim spouted water is directly supplied as water main water from a rim water spouting port, whereas jet spouted water is flush water stored in a tank and pressurized by a pump, with this pressurized flush water then being expelled from a jet water spouting port to flush the bowl portion.
In the flush toilet set forth in JP2005-264469 (Patent Document 2), on the other hand, flush water is first spouted from a rim water spouting port (rim flushing), then, after spouting from the rim water spouting port is completed, flush water is spouted from a jet water spouting port, and when spouting from the jet water spouting port is completed, flush water is again spouted from the rim water spouting port.
However, because the flush toilet set forth in Patent Document 1 supplies flush water to the toilet bowl portion using water main pressure alone, it cannot be used in localities with low water main pressure, or on the second or third floors of buildings and the like where water pressure is lower. Also, in this type of flush toilet, after the siphon action ended a relatively large volume of air was sucked from the trap pipe producing an unpleasant gurgling sound as the siphon action was cut off.
In the flush toilet set forth in Patent Document 2, flush water stored in the tank is pressurized by a pump and expelled from a jet water spouting port, thus solving the problem of non-usability in low water pressure localities or sites, but the noise problem remained unsolved.
In addition, there has long been a requirement for water conservation, and a desire for low water-use flush toilets.
At the same time, as noted above, in the flush toilet of Patent Document 2 flush water is spouted from the jet water spouting port after spouting of flush water from the rim water spouting port is completed, but because the volume of jet spouted water is low, a long time is required until the siphon effect is generated (siphon start), increasing flush water volume by that amount, such that the water conservation requirement is not satisfied.
Furthermore, as described above, in the Patent Document 1 flush toilet both the rim water spouting port and the jet water spouting port are directly connected to the water main. For this reason, the volume of flush water supplied from the water main is fixed when flush water is spouted from the jet water spouting port during spouting from the rim water spouting port (see FIG. 29 in Patent Document 1), therefore the volume of rim spout water must be reduced when spouting flush water from the jet water spouting port, resulting in less jet spouted water, thereby lengthening the time until the siphon effect is generated (siphon start), as in Patent Document 2, causing an increase by that amount in the volume of flush water and failing to satisfy the requirement for water conservation.